When using liquid hydrocarbons as lubricating oils or fuels, it is necessary that the hydrocarbon fluids flow readily at low temperatures, especially at temperatures below the freezing point of water (0.degree. C.). The flow of these fluids, particularly those with high wax content, is very sensitive to low temperatures. At low temperature when the wax crystallizes, the fluid sets up as a waxy material and does not pour. The pour point depressant additives do not reduce the amount of wax which crystallizes from the fluids, but rather modify their surface by absorption or co-crystallization. This reduces the fluid occlusion by the crystals and changes the wax crystal structure, thus permitting the fluid to flow.
Major types of materials that have found wide acceptance as pour point depressants are naphthylene alkylated with chlorinated waxes and homo- or copolymers of hydrocarbon olefins, methacrylates, vinyl esters and alkyl styrene.